Slurry Sand Content and Concrete Interaction in Drilled Shaft Construction

• Main Author: Deese, Gregory Gene
• Format: Others
• Published: Scholar Commons 2004
• Subjects: bentonite; deep foundation; caisson; quality assurance; filter cake; American Studies; Arts and Humanities
• Online Access: https://scholarcommons.usf.edu/etd/1010; https://scholarcommons.usf.edu/cgi/viewcontent.cgi?article=2009&context=etd

Due to the widespread use of drilled shafts in state and federal highway bridges, strict regulation of the design and construction has been imposed by the respective agencies. However, documented cases of anomalies and/or poorly performing shafts continue to arise. To this end, this thesis investigates several aspects of drilled shaft construction that may affect the quality of the finished product. These areas include bentonite slurry properties and performance as well as reinforcement cage and concrete flow interactions. Recent research indicates tremie poured concrete does not flow as predicted. Instead of even rising, a differential between the height of concrete inside and outside the reinforcement cage has been observed. Compounding this problem is the fact that bentonite slurry used to support boreholes may settle suspended sand at the toe of the shaft or on the surface of rising concrete during long wait periods, affording the possibility of soil inclusions in the shaft. This thesis examines two methods of inquiry to quantify the behavior of concrete in a tremie pour drilled shaft and sand suspension behavior of bentonite slurry. Conclusions and recommendations are made to improve pertinent construction regulations to ensure quality of drilled shafts.